Question

phase 3:
diffusion rate in a semisolid
complete the following steps:
1 add one crystal to agar dish using tweezers
2 wait 15 minutes
3 measure the diffusion spot diameter. record in lab data
4 calculate average diffusion rate from time zero in mm/h. record in lab data

Explanation:

Measure the diffusion spot diameters

Using the Diffusion Measurement knowledge point

• Left dish (red/brown spot): The spot is centered at approximately \(0.8\text{ cm}\). It extends from \(0.3\text{ cm}\) to \(1.3\text{ cm}\).

$$ \text{Diameter}_{\text{red}} = 1.3\text{ cm} - 0.3\text{ cm} = 1.0\text{ cm} = 10\text{ mm} $$

• Right dish (blue/purple spot): The spot is centered at approximately \(11.7\text{ cm}\). It extends from \(11.5\text{ cm}\) to \(11.9\text{ cm}\).

$$ \text{Diameter}_{\text{blue}} = 11.9\text{ cm} - 11.5\text{ cm} = 0.4\text{ cm} = 4\text{ mm} $$

Calculate average diffusion rates

Using the Diffusion Rate Calculation knowledge point

• Elapsed time: \(15\text{ minutes} = 0.25\text{ hours}\).
• Red dye diffusion rate:

$$ \text{Rate}_{\text{red}} = \frac{10\text{ mm}}{0.25\text{ h}} = 40\text{ mm/h} $$

• Blue dye diffusion rate:

$$ \text{Rate}_{\text{blue}} = \frac{4\text{ mm}}{0.25\text{ h}} = 16\text{ mm/h} $$

Answer:

Question 1: Diffusion Spot Diameters

• Red/Brown Dye (Left Dish): \(10\text{ mm}\) (or \(1.0\text{ cm}\))
• Blue/Purple Dye (Right Dish): \(4\text{ mm}\) (or \(0.4\text{ cm}\))

Question 2: Average Diffusion Rates

• Red/Brown Dye (Left Dish): \(40\text{ mm/h}\)
• Blue/Purple Dye (Right Dish): \(16\text{ mm/h}\)